CAROTID MAGNETIC-RESONANCE ANGIOGRAPHY - IMPROVED IMAGE QUALITY WITH DUAL 3-INCH SURFACE COILS

Magnetic resonance angiography (MRA) hs inherent artifacts due to vari ation in velocity and direction of flowing blood in the carotid bulb a nd regions of stenosis. We examined the efficiency of dual 3-inch surf ace coils to delineate carotid artery flow better. Carotid MRA was per formed on ten healthy volunteers and six patients, on a 1.5 T system, A special adapter was constructed to use with 3-inch (receive-only) co ils, which were placed over the carotid bifurcations, Routine anterior neck coils were also used. Contiguous axial two-dimensional (45/8.7, 1.5 mm, flip angle 60 degrees) time-of-flight sequences were used. Ima ge matrix was 256 x 256 with two signals averaged and acquisition time 6-10 min, These images were postprocessed and reformatted into angiog raphic views using a maximum intensity projection algorithm. Computer simulation of carotid artery blood flow throughout the cardiac cycle b ased on vessel contours derived from digital subtraction angiography w as carried out by finite element analysis, Improved definition of vess el margin, particularly at the carotid bifurcation, and substantially increased signal-to-background ratio of flowing blood were obtained wi th 3-inchcoils. Apparent loss of signal in the carotid bulb was dimini shed. In one patient, contiguous flow throughout a high-grade stenosis was well defined, with the surface coil method, while drop-off of sig nal was observed with routine neck coil imaging.